Re: [PATCH] ata: libata: disallow dev-initiated LPM transitions to unsupported states

[Damien Le Moal <dlemoal@kernel.org>]

On 9/5/23 05:42, Niklas Cassel wrote:
> From: Niklas Cassel <niklas.cassel@wdc.com>
> 
> In AHCI 1.3.1, the register description for CAP.SSC:
> "When cleared to ‘0’, software must not allow the HBA to initiate
> transitions to the Slumber state via agressive link power management nor
> the PxCMD.ICC field in each port, and the PxSCTL.IPM field in each port
> must be programmed to disallow device initiated Slumber requests."
> 
> In AHCI 1.3.1, the register description for CAP.PSC:
> "When cleared to ‘0’, software must not allow the HBA to initiate
> transitions to the Partial state via agressive link power management nor
> the PxCMD.ICC field in each port, and the PxSCTL.IPM field in each port
> must be programmed to disallow device initiated Partial requests."
> 
> Ensure that we always set the corresponding bits in PxSCTL.IPM, such that
> a device is not allowed to initiate transitions to power states which are
> unsupported by the HBA.
> 
> DevSleep is always initiated by the HBA, however, for completeness, set the
> corresponding bit in PxSCTL.IPM such that agressive link power management
> cannot transition to DevSleep if DevSleep is not supported.
> 
> sata_link_scr_lpm() is used by libahci, ata_piix and libata-pmp.
> However, only libahci has the ability to read the CAP/CAP2 register to see
> if these features are supported. Therefore, in order to not introduce any
> regressions on ata_piix or libata-pmp, create flags that indicate that the
> respective feature is NOT supported. This way, the behavior for ata_piix
> and libata-pmp should remain unchanged.
> 
> This change is based on a patch originally submitted by Runa Guo-oc.
> 
> Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>

Applied to for-6.6-fixes. Thanks !


-- 
Damien Le Moal
Western Digital Research